Novel 1,3,5-tris(arylamino)benzene

ABSTRACT

The invention provides 1,3,5-tris(arylamino)benzenes represented by the general formula (I)  
                 
wherein A is naphthyl, anthryl, phenanthryl, biphenylyl or terphenylyl group, and R is alkyl having 1-6 carbon atoms or cycloalkyl group having five or six carbon atoms. The 1,3,5-tris(arylamino)benzenes have oxidation potentials in the range of about 0.5-0.6V, excellent reversibility in oxidation-reduction process and high glass transition temperatures and in addition, they are capable of forming stable and durable amorphous film useful as high performance organic semiconductors at normal temperatures or higher with no aid of binder resins, that is, by themselves.

FIELD OF THE INVENTION

This invention relates to novel 1,3,5-tris(arylamino)-benzenes useful asorganic semiconductors. More particularly, the invention relates tonovel 1,3,5-tris(arylamino)benzenes that are superior in reversibilityof oxidation-reduction process and can form stable organic semiconductorfilm readily by a coating method or a vacuum deposition method.Accordingly they are suitable for use as organic semiconductors in avariety of electronic devices such as electric charge transport agentsin electrophotographic devices or organic semiconductors in solarbatteries.

BACKGROUND ART

In recent years, organic semiconductors comprised of amorphous film oforganic substances are in wide use in a variety of electronic devices.For example, an organic amorphous film is formed by preparing a coatingcomposition comprised of a binder resin such as polycarbonate resin anda low molecular weight organic compound such as a triphenylaminederivative having photoelectric function dissolved in a suitable organicsolvent and then by coating and drying the composition. The film thusformed is used as a positive hole transport layer in electrophotographicdevices, as described in JP-A-1999-174707. Similarly, an organicamorphous film is formed by preparing a coating composition comprised ofa so-called star-burst compound dissolved in a suitable organic solventand then by coating and drying the composition. The film thus formed isused as an organic p-type semiconductor film in solar batteries, asdescribed in JP-A-2000-174657.

As described above, organic semiconductor films comprised of organicamorphous film have been prepared by preparing a coating compositionusing a low molecular weight organic compound having photoelectricfunction together with a binder resin and then coating the compositionon a suitable substrate and drying the composition. However, many of thelow molecular weight organic compounds that have hitherto been knownhave low oxidation potentials, and accordingly when they are formed toorganic semiconductor films by a coating method, they are easilyoxidized, so that it is not easy to form a film using such low molecularweight organic compounds. They have also no sufficient reversibility inoxidation-reduction process so that it is difficult to prepare organicsemiconductor film durable and suitable for practical use. In addition,the resulting organic semiconductor films have no sufficient heatresistance and hence the electronic devices using such organicsemiconductor films are inferior in stability and durability.

As typical low molecular weight organic compounds that havephotoelectric function and are usable for preparing organicsemiconductor films, there have been known such compounds asN,N,N′,N′-tetramethylbenzidine,N,N,N′,N′-tetraphenyl-(1,1′-biphenyl)-4,4′-diamine,N,N′-diethyl-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine, orN,N,N′,N′-tetra(3-methylphenyl)-4,4′-diaminostilbene. However, these lowmolecular weight organic compounds form only amorphous films that are bythemselves not so stable as to be used as electric charge transportagents in organic photosensitive elements. Accordingly, they aredispersed in a binder resin (that is, diluted with a binder resin), andthe resulting dispersion is applied to a substrate to form an amorphousfilm.

Thus, the known low molecular weight organic compounds that form anorganic amorphous film are diluted with a binder resin and areinfluenced by the binder resin which forms a matrix for the amorphousfilm so that the organic amorphous film cannot exhibit sufficiently theproperties that they originally possess. In addition, if the known lowmolecular weight organic compounds form an amorphous film that isrelatively stable at normal temperatures with the aid of a binder, theyhave low glass transition temperatures so that the film is poor in heatresistance and is not suitable for practical use.

Accordingly, the development of low molecular weight organic compoundsthat have photoelectric conversion function and are capable of formingamorphous film by themselves at normal temperatures or higher has beenpushed on with in recent years, and as results, some nitrogen-containingpolynuclear aromatic compounds called star-burst molecules have beenproposed as such low molecular weight organic compounds.

The star-burst molecules are divided into three groups based on theirmolecular structures: compounds having triphenylamine structure(triphenylamines), compounds having triaminobenzene structure(triaminobenzenes) and compounds having triphenylbenzene structure(triphenylbenzenes). Beside the above-mentioned, compounds havingtriphenylmethane structure are also proposed.

The triphenylamines include, for example,4,4′,4″-tris-(N,N-diphenylamino)triphenylamine (TDATA) (1) having thestructure

as described in JP-A-1990-224353;4,4′,4″-tris(N-phenyl-N-m-tolylamino)triphenylamine (m-MTDATA) (2)having the structure

as described in JP-A-1990-224353;4,4′,4″-tris(N-(2-naphthyl)-N-phenylamino)triphenylamine (2-TNATA) (3)having the structure

as described in JP-A-1996-291115; and4,4′,4″-tris(N-(1-naphthyl)-N-phenylamino)triphenylamine (1-TNATA).

These triphenylamines are reversible in oxidation-reduction process,however, they have low oxidation potentials (oxidation potential againstAg/Ag⁺ electrode, the same hereunder) of about 0.1V or less so thatthere is a problem in that they are easily oxidized when they are formedto organic semiconductor film by a coating method.

m-MTDATA has a glass transition temperature of about 77° C. so that itis difficult to use the compound in practical electronic devices, and onthe other hand, 2- or 1-TNATA has a glass transition temperature ofabout 110° C. and is capable of forming heat-resistant organic amorphousfilm, but the compound is readily crystallized so that the resultingorganic amorphous film is lacking in stability or durability.

The triphenylbenzenes include, for example,1,3,5-tris(4-(N,N-diphenylaminophenyl)benzene (TDAPB) having thestructure (4)

and 1,3,5-tris(4-(N-tolyl-N-phenylaminophenyl)benzene (MTDAPB) (5)having the structure

as described in Bando Technical Report, Vol. 2, pp. 9-18, 1998 (BandoChemical Industries, Ltd.).

The triphenylbenzenes are capable of forming amorphous film and haveoxidation potentials in the range of 0.6-0.7V, but they are irreversiblein oxidation-reduction process so that they are not suitable for use inpractical use as organic semiconductors.

In turn, the triaminobenzenes include, for example,1,3,5-tris(N-methylphenyl-N-phenylamino)benzene (MTDAB) having thestructure (6)

as described in Bando Technical Report, Vol. 2, pp. 9-18, 1998 (BandoChemical Industries, Ltd.). The triaminobenzenes also have oxidationpotentials in the range of 0.5-0.6V, but they are irreversible inoxidation-reduction process, like the above-mentioned triphenylbenzenes,and in addition, they have glass transition temperatures as low as about60° C. or less so that they are not suitable for use in practical use asorganic semiconductors. They have further problems in heat resistance.

The invention has been accomplished to solve the above-mentionedproblems in the star-burst molecules having triaminobenzene structurefor use as materials for organic semiconductors.

Accordingly, it is an object of the invention to provide novel1,3,5-tris(arylamino)benzenes that have oxidation potentials in therange of about 0.5-0.6V and high glass transition temperatures and thatare superior in reversibility in oxidation-reduction process and heatresistance so that they are readily formed to organic semiconductor filmby a coating method or vacuum deposition method, as well as they arecapable of forming stable and durable high-performance organicsemiconductor film by themselves because they are capable of formingamorphous film by themselves with no aid of binder resins at normaltemperatures or higher.

SUMMARY OF THE INVENTION

The invention provides 1,3,5-tris(arylamino)benzenes represented by thegeneral formula (I)

wherein A is naphthyl, anthryl, phenanthryl, biphenylyl or terphenylylgroup, and R is alkyl having 1-6 carbon atoms or cycloalkyl group havingfive or six carbon atoms.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is an infrared absorption spectrum of1,3,5-tris-(N-(p-methylphenyl)-N-(1-naphthyl)amino)benzene (p-MTPNAB) ofthe invention;

FIG. 2 is a differential scanning calorimetry (DSC) curve of1,3,5-tris(N-(p-methylphenyl)-N-(1-naphthyl)amino)-benzene (p-MTPNAB) ofthe invention;

FIG. 3 is a cyclic voltamogram of1,3,5-tris(N-(p-methylphenyl)-N-(1-naphthyl)amino)benzene (p-MTPNAB) ofthe invention;

FIG. 4 is a fluorescence spectrum of1,3,5-tris(N-(p-methylphenyl)-N-(1-naphthyl)amino)benzene (p-MTPNAB) ofthe invention;

FIG. 5 is an infrared absorption spectrum of1,3,5-tris-(N-(p-tert.-butylphenyl)-N-(1-naphthyl)amino)benzene of theinvention;

FIG. 6 is a differential scanning calorimetry (DSC) curve of1,3,5-tris(N-(p-tert.-butylphenyl)-N-(1-naphthyl)amino)-benzene of theinvention;

FIG. 7 is a cyclic voltamogram of1,3,5-tris(N-(p-tert.-butylphenyl)-N-(1-naphthyl)amino)benzene of theinvention;

FIG. 8 is an infrared absorption spectrum of1,3,5-tris-(N-(p-methylphenyl)-N-(4-biphenylyl)amino)benzene (p-MTPBAB)of the invention;

FIG. 9 is a differential scanning calorimetry (DSC) curve of1,3,5-tris(N-(p-methylphenyl)-N-(4-biphenylyl)amino)-benzene (p-MTPBAB)of the invention;

FIG. 10 is a cyclic voltamogram of1,3,5-tris(N-(p-methylphenyl)-N-(4-biphenylyl)amino)benzene (p-MTPBAB)of the invention; and

FIG. 11 is a fluorescence spectrum of1,3,5-tris(N-p-methylphenyl)-N-(4-biphenylyl)amino)benzene (p-MTPBAB) ofthe invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The 1,3,5-tris(arylamino)benzenes of the invention are expressed by thegeneral formula (I)

wherein A is naphthyl, anthryl, phenanthryl, biphenylyl or terphenylylgroup, preferably 1- or 2-naphthyl, 1-, 2- or 9-anthryl, 1-, 2-, 3-, 4-or 9-phenanthryl, 2-, 3- or 4-biphenylyl, or 2-, 3-, 4-2″- or3″-terphenylyl group. In particular, it is preferred that A is 1- or2-naphthyl, 9-phenanthryl, 4-biphenylyl or 4-p-terphenylyl group.

According to the invention, the naphthyl, anthryl, phenanthryl,biphenylyl or terphenylyl group may carry substituents thereon that giveno harmful influence on oxidation potentials, reversibility ofoxidation-reduction process or glass transition temperatures of thedesired 1,3,5-tris(arylamino)-benzenes. Such substituents include, forexample, alkyl groups, alkoxy groups, aryloxy groups, aralkyl groups,alkyl aryl groups, primary, secondary or tertiary amino groups, nitrogroups, cyano groups or halogen atoms. However, it is preferred that1,3,5-tris-(arylamino)benzenes of the invention have 1- or 2-naphthylgroup or 4-biphenylyl group that carry no such substituents thereon.

Further according to the invention, in the1,3,5-tris-(arylamino)benzenes represented by the general formula (I), Ris an alkyl group of 1-6 carbon atoms or a cycloalkyl group of five orsix carbon atoms, and more particularly, the alkyl group is methyl,propyl, butyl, pentyl or hexyl group. When the alkyl group has three ormore carbon atoms, it may be either linear or branch. On the other hand,the cycloalkyl group is cyclopentyl or cyclohexyl group. However, R ispreferably a methyl or tert.-butyl group.

The 1,3,5-tris(arylamino)benzenes of the invention is obtained by thereaction of 1,3,5-tris(p-alkylphenylamino)benzenes represented by thegeneral formula (II)

wherein R is the same as the above with an aryl halide represented bythe general formula (III)A-X  (III)wherein A is the same as above and X is a halogen atom, depending on the1,3,5-tris(arylamino)benzene to be obtained, in the presence of a baseand copper powder under an atmosphere of inert gas such as nitrogen,argon or helium using a crown compound such as 18-crown-6 (or1,4,7,10,13,16-hexaoxacyclooctadecane) as a catalyst, if necessary, in asolvent.

The aryl halides preferably used are, for example, iodides or bromides.If necessary, chlorides are also used. By way of example, when1,3,5-tris(N-(p-methylphenyl)-N-(1-naphthyl)-amino)benzene (p-MTPNAB) or1,3,5-tris(N-(p-tert.-butylphenyl)-N-(1-naphthyl)amino)benzene is to beobtained, 1-iodonaphthalene is preferably used as the aryl halide, andon the other hand, when1,3,5-tris(N-(p-methylphenyl)-N-(4-biphenylyl)amino)benzene (p-MTPBAB)is to be obtained, 4-iodobiphenyl is preferably used as the aryl halide.

The aryl halides are used in excess in relation to1,3,5-tris(p-alkylphenylamino)benzene. More particularly, the arylhalides are used preferably in an amount of more than three mole partsin relation to mole part of 1,3,5-tris(p-alkylphenyl-amino)benzene, andmore preferably in an amount of 3-10 mole parts, and most preferably inan amount of 3.5-5 mole parts in relation to mole part of1,3,5-tris(p-alkylphenyl-amino)-benzene.

The bases used in the reaction include, for example, hydroxides ofalkali metals such as potassium hydroxide, or carbonates or hydrogencarbonates of alkali metals, especially those of sodium or potassium,and in particular, potassium carbonate is preferred. In the reaction,any solvent may be used so far as it does not inhibit the reaction, andusually hydrocarbon solvents such as decalin, mesitylene or heptane arepreferably used. The reaction temperature is not specifically limited,but it is usually in the range of 140-190° C., and the reaction time isusually in the range of 5-30 hours.

After the completion of reaction, the reaction product is dissolved inan organic solvent and the catalyst used is separated by filtration, andthen the reaction product is separated and purified by columnchromatography using an appropriate eluate to provide a high purityproduct in high yields.

The 1,3,5-tris(arylamino)benzenes of the invention have oxidationpotentials in the range of about 0.5-0.6V. From the structural point ofview, in the first place, they have a skeleton of1,3,5-tris(arylamino)benzene in which one of the substituents on each ofnitrogen atoms is p-alkylphenyl group, so that the p-alkylphenylsubstituent covers the active cite of the compound thereby securing thereversibility in oxidation-reduction process. In the second place, saideach of nitrogen atoms carries naphthyl, anthryl, phenanthryl,biphenylyl or terphenylyl group thereon as a substituent so that thecompound has high glass transition temperatures and hence high heatresistance, and in addition, the compound has improved reversibility inoxidation-reduction reaction.

As described above, the 1,3,5-tris(arylamino)benzenes of the inventionare suitably used for preparation of organic semiconductor film that issuperior in stability and heat resistance. Furthermore, the1,3,5-tris(arylamino)benzenes of the invention are capable of formingamorphous film by themselves at normal temperatures or higher, and hencethey are capable of forming high-performance durable organicsemiconductor film by themselves.

Accordingly, the 1,3,5-tris(arylamino)benzenes of the invention aresuitably used as elements in various electronic devices such as chargetransport agents in electrophotography or organic semiconductors insolar batteries, although they are not specifically limited in theiruse.

EXAMPLE

The invention is described in more detail with reference to examples,however, the invention is not limited thereto.

Example 1 Synthesis of 1,3,5-tris(p-tolylamino)benzene

11.8 g of phloroglucinol, 50 g of p-toluidine and 0.5 g of iodine wereplaced in a 300 mL capacity three necked flask and the reaction wascarried out at a temperature of 150° C. for 15 hours with stirring undera nitrogen atmosphere. After the reaction, the resultant reactionmixture was washed with methanol, hexane and methanol in this order,followed by drying to provide the desired1,3,5-tris(p-tolylamino)benzene as slightly reddish solid. The yield was86.5%.

Synthesis of 1,3,5-tris(N-(p-methylphenyl)-N-(1-naphthyl)amino)-benzene(p-MTPNAB)

2.0 g of 1,3,5-tris(p-tolylamino)benzene, 6.4 g of 1-iodo-naphthalene,6.9 g of potassium carbonate, 11.0 g of copper powder, 0.7 g of18-crown-6 (or 1,4,7,10,13,16-hexaoxacyclooctadecane) and 15 mL ofmesitylene were placed in a 100 mL capacity glass flask and the reactionwas carried out at a temperature of 170° C. for 18 hours under anitrogen atmosphere. After the reaction, the resultant reaction mixturewas extracted with toluene and the toluene solution was subjected tosilica gel chromatography to fractionate the reaction product. Thereaction product was then purified by recrystallization and then bysublimation to provide 2.2 g of the desired1,3,5-tris(N-(p-methylphenyl)-N-(1-naphthyl)-amino)benzene (p-MTPNAB).The yield was 57%.

Elemental Analysis (%): C H N Calculated: 88.68 5.88 5.44 Measured:88.58 6.00 5.43Mass analysis: M⁺ = 771Infrared absorption spectrum is shown in FIG. 1.Differential Scanning Calorimetry (DSC):

About 5 mg of p-MTPNAB was weighed as a sample, and it was melted in adifferential scanning calorimetric device and cooled to room temperatureat a rate of 50° C. per minute. The sample did not crystallized, but itbecame amorphous glass. Subsequently, the thermal characteristics of thesample were measured by heating at a rate of 50° C. per minute by usingan aluminum plate as a reference. As the DSC chart is shown in FIG. 2,the compound was found to have a glass transition temperature (Tg) of87° C. and a crystallization temperature (Tc) of 167° C.

Cyclic Voltammetry (CV):

p-MTPNAB was dissolved in dichloromethane and the solution was arrangedat a concentration of 10⁻³ M. The oxidation reduction characteristics ofthe sample were measured using tetrabutylammonium perchlorate((n-C₄H₉)₄NClO₄ (0.1M)) as a supporting electrolyte and Ag/Ag⁺ as areference electrode at a scan speed of 50 mV/s. As the CV chart is shownin FIG. 3, the compound has an oxidation potential of 0.6V (vs. Ag/Ag⁺).It was found that the compound had reversibility in oxidation reductionprocess after 50 times measurements, indicating that the compound issuitably used as organic positive hole transport agents.

Fluorescence Spectrum:

A deposition film (an amorphous film) 500 Å thick was prepared by usinga vacuum deposition apparatus, and the film was subjected to measurementof fluorescence spectrum using excitation light of a wavelength of 320nm. As the spectrum is shown in FIG. 4, the compound has an emissionpeak at 435.4 nm.

Example 2 Synthesis of 1,3,5-tris(p-tert.-butylphenylamino)benzene

4.0 g of phloroglucinol, 23.8 g of p-tert.-butylaniline and 0.2 g ofiodine were placed in a 100 mL capacity three necked flask and thereaction was carried out at a temperature of 160° C. for 2.5 hours withstirring under a nitrogen atmosphere. After the reaction, the resultantreaction mixture was washed with hexane and then recrystallized frommethyl ethyl ketone/ethanol, followed by drying to provide 7.4 g of thedesired 1,3,5-tris(p-tert.-butyl-phenylamino)benzene as white solid. Theyield was 44.7%.

(Synthesis of1,3,5-tris(N-(p-tert.-butylphenyl)-N-(1-naphthyl)-amino)benzene)

2.6 g of 1,3,5-tris(p-tert.-butylphenylamino)benzene, 6.4 g of1-iodonaphthalene, 6.9 g of potassium carbonate, 11.0 g of copperpowder, 0.7 g of 18-crown-6 (or 1,4,7,10,13,16-hexaoxacyclo-octadecane)and 20 mL of mesitylene were placed in a 100 mL capacity flask and thereaction was carried out at a temperature of 170° C. for 16.5 hoursunder a nitrogen atmosphere. After the reaction, the resultant reactionmixture was extracted with toluene and the toluene solution wassubjected to silica gel chromatography to fractionate the reactionproduct. The reaction product was then purified by recrystallization andthen by sublimation to provide 2.8 g of the desired1,3,5-tris(N-(p-tert.-butylphenyl)-N-(1-naphthyl)amino)-benzene. Theyield was 62%.

Elemental Analysis (%): C H N Calculated: 88.25 7.07 4.68 Measured:88.23 7.18 4.65Mass analysis: M⁺ = 897Infrared absorption spectrum is shown in FIG. 5.Differential Scanning Calorimetry (DSC):

About 5 mg of1,3,5-tris(N-(p-tert.-butylphenyl)-N-(1-naphthyl)amino)benzene wasweighed as a sample, and it was melted in a differential scanningcalorimetric device and cooled to room temperature at a rate of 50° C.per minute. The sample did not crystallized, but it became amorphousglass. Subsequently, the thermal characteristics of the sample weremeasured by heating at a rate of 5° C. per minute by using an aluminumplate as a reference. As the DSC chart is shown in FIG. 6, the compoundhas a glass transition temperature (Tg) of 118° C. and a crystallizationtemperature (Tc) of 170° C.

Cyclic Voltammetry (CV):

1,3,5-tris(N-(p-tert.-butylphenyl)-N-(1-naphthyl)amino)-benzene wasdissolved in dichloromethane and the solution was arranged at aconcentration of 10⁻³ M. The oxidation reduction characteristics of thesample were measured using tetrabutylammonium perchlorate((n-C₄H₉)₄NClO₄ (0.1M)) as a supporting electrolyte and Ag/Ag⁺ as areference electrode at a scan speed of 10 mV/s. As the CV chart is shownin FIG. 7, the compound has an oxidation potential of 0.6V (vs. Ag/Ag⁺).It was found that the compound had reversibility in oxidation reductionprocess after 50 times measurements, indicating that the compound issuitably used as organic positive hole transport agents.

Example 3 Synthesis of 1,3,5-tris(p-tolylamino)benzene

11.8 g of phloroglucinol, 50 g of p-toluidine and 0.5 g of iodine wereplaced in a 300 mL capacity three necked flask and the reaction wascarried out at a temperature of 150° C. for 15 hours with stirring undera nitrogen atmosphere. After the reaction, the resultant reactionmixture was washed with methanol, hexane and methanol in this order,followed by drying to provide 31.9 g of the desired1,3,5-tris(p-tolylamino)benzene as slightly reddish solid. The yield was86.5%.

Synthesis of1,3,5-tris(N-(p-methylphenyl)-N-(4-biphenylyl)-amino)benzene (p-MTPBAB)

2.0 g of 1,3,5-tris(p-tolylamino)benzene, 7.0 g of 4-iodo-biphenyl, 6.9g of potassium carbonate, 11.0 g of copper powder, 0.7 g of 18-crown-6(or 1,4,7,10,13,16-hexaoxacyclooctadecane) and 15 mL of mesitylene wereplaced in a 100 mL capacity glass flask and the reaction was carried outat a temperature of 170° C. for 15 hours under a nitrogen atmosphere.After the reaction, the resultant reaction mixture was extracted withtoluene and the toluene solution was subjected to silica gelchromatography to fractionate the reaction product. The reaction productwas then purified by recrystallization and then by sublimation toprovide 2.2 g of the desired1,3,5-tris(N-(p-methylphenyl)-N-(4-biphenylyl)amino)-benzene (p-MTPBAB).The yield was 16%.

Elemental Analysis (%): C H N Calculated: 89.07 5.91 5.03 Measured:88.87 6.09 4.95Mass analysis: M⁺ = 849Infrared absorption spectrum is shown in FIG. 8.Differential Scanning Calorimetry (DSC):

About 5 mg of p-MTPBAB was weighed as a sample, and it was melted in adifferential scanning calorimetric device and cooled to room temperatureat a rate of 50° C. per minute. The sample did not crystallized, but itbecame amorphous glass. Subsequently, the thermal characteristics of thesample were measured by heating at a rate of 5° C. per minute by usingan aluminum plate as a reference. As the DSC chart is shown in FIG. 9,the compound has a glass transition temperature (Tg) of 98° C. and acrystallization temperature (Tc) of 145° C.

Cyclic Voltammetry (CV):

p-MTPBAB was dissolved in dichloromethane and the solution was arrangedat a concentration of 10⁻³ M. The oxidation reduction characteristics ofthe sample were measured using tetrabutylammonium perchlorate((n-C₄H₉)₄NClO₄ (0.1M)) as a supporting electrolyte and Ag/Ag⁺ as areference electrode at a scan speed of 50 mV/s. As the CV chart is shownin FIG. 10, the compound has an oxidation potential of 0.6V (vs.Ag/Ag⁺). It was found that the compound had reversibility in oxidationreduction process after 50 times measurements, indicating that thecompound is suitably used as organic positive hole transport agents.

Fluorescence Spectrum:

A deposition film (an amorphous film) 500 Å thick was prepared using avacuum deposition apparatus, and the film was subjected to measurementof fluorescence spectrum using excitation light of a wavelength of 320nm. As the spectrum is shown in FIG. 11, the compound has an emissionpeak at 415.0 nm.

INDUSTRIAL APPLICABILITY OF THE INVENTION

The invention provides novel 1,3,5-tris(arylamino)-benzenes. They haveoxidation potentials in the range of about 0.5-0.6V and an excellentreversibility in oxidation-reduction process, as well as high glasstransition temperatures and excellent heat resistance, and hence theyreadily form amorphous film useful as organic semiconductors by acoating method or a vacuum deposition method. In addition, the1,3,5-tris-(arylamino)benzenes of the invention are capable of formingamorphous film by themselves at normal temperatures or higher so thatthey find wide applications as organic amorphous materials in a varietyof fields, such as electric charge transport agents inelectrophotography or organic semiconductors in solar batteries.

1. A 1,3,5-tris(arylamino)benzene represented by the general formula (I)

wherein a is naphthyl, anthryl, phenanthryl, biphenylyl or terphenylylgroup, and R is alkyl having 1-6 carbon atoms or cycloalkyl group havingfive or six carbon atoms. 2.1,3,5-tris(N-(p-methylphenyl)-N-(1-naphthyl)amino)benzene. 3.1,3,5-tris(N-(p-tert.-butylphenyl)-N-(1-naphthyl)amino)-benzene. 4.1,3,5-tris(N-(p-methylphenyl)-N-(4-biphenylyl)amino)benzene.